What I'd have to do after connecting the view's resize event to the delegate is basically to emit sizeHintChanged signals for the whole of my model. That just doesn't appear to be the "right" way to do it, does it?
After all, the cause for the update is completely "external", not something in the data itself (which is what I think that the delegate's sizeHintChanged signal is probably intended for).

Isn't there a way to just tell the view to recalculate its items' sizes? It works for 'growing' items already... Maybe I could try to simulate a model-reset with saving/restoring the view's selection-state if there isn't a "best practice way"? All of this seems to be rather hackish though. It thought there has to be a "clean" way to do it...